Control circuit



May 8, 1962 SIGUZSKIE ET AL CONTROL CIRCUIT 2- Shee'hs-Sheea 1 Filed June 2, 1958 INVENTORS.

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CONTROL CIRCUIT Filed June 2, 1958 T 2 Sheets-Sheet 2 STEPPING SWITCH MECHANICAL LINKAGE RECEIVER AND TRANSDUCER INVENTORS Ufa/ends J fz/pucii fanfey Gu skie Meyer .flfar' TRANSMITTER HIS A TT OlP/VE Y United States Patent 3,033,930 I CONTRQL CIRCUIT Stanley Guzskie, Broadview, Clarence J. Holpuch, Chi 'cago, and Meyer Marks, Clarendon Hills, Ill., assignors to Admiral Corporation, (Zhica'go, Ilk, a corporation of Delaware Filed June 2, 1958, filer. No. 739,374

. 4 Claims. (Cl. 179-1) This invention relates generally to power control switches and more particularly to means for controlling remotely the power delivered to a load, suchas, for er;- ample, a speaker.

There are in 'the p'rior art many different examples or" remotely controlled power control circuits. Some of these control circuits function to change the bias on a vacuum tube; others function to vary an impedance connected in parallel with the utilization means, and others employ more elaborateschemes.

It is desirable, when supplying asignal from a source to a utilization means (such as a speaker), to match the output impedance of the signal sourcewith the input impcdance of the utilization means in order to obtain maximum power transfer and toy minimize distortion. In systerns employing a variable impedance connected across the input terminals of the load, it is desirable to maintain the matching of such impedances as closely as possible while altering the amount of power supplied to the utilization means. While many of the prior art remote volume COIltIOl systems function to change the a ount er powersuppliedrto the speaker (or other utilization means) only the more elaborate systems function to maintain a nearcofistan't load input impedance (to match the power source output impedance) and thus minimize distor-titan.

A object of the present invention is to provide a simple system for remotely'controlling the power delivered to a speaker or other utilization means but which minimizes distortion.

, A se'cond'object of the invention is to provide means for controlling remotely the power delivered from a signal source to a utilization means while maintaining,

- within fairly close tolerances, the overall impedance presented tothe signal source.

Another aim of the invention is a remote volume control of simple construction butcapable of maintaining,

impedance means connected to a first input terminal of the utilization means and in series therewith. A switch havingfirst and second stationary contact means and a first movable contact is constructed and arranged to shunt said first impedance means when said movable contact is closed on said first contact means. Located remotel'y from the utilization means are third stationary contact means, second impedance means having a plurarity of co'n'tactable points thereon, a second movable contact constructed and arranged to contact selectively said third contact means or any of said contactable points on said second impedance means, means for connecting said third contact means to said first contact means to enable shunting of said first impedance means from the remote position, means for connecting said second movable contact to said second contact means, and means for connecting one end terminal of said second pedance mean to the second input terminal of the utilization means.

In accordance with a feature of the invention a stepbetween the remote control unit and the speaker since all the elements except the portable transmitter can be located near the utilization means (the speaker when the device is employed as a volume control).

The above mentioned and other objects and features of the invention will be understood more fully from the following detailed description thereof when read in conjunction with the drawings in which:

FIG. 1 is a schematic sketch of a preferred embodiment of the invention;

FIG. 2, is a schematic sketch of an alternative form of the invention;

FIG. 3 is a combination block diagram and schematic sketch of another form of the invention; and i FIG. 4 is. a modification of the circuit of FIG. 1.

It is to be understood that the invention about to be described has many applications and that one of the more common applications is as a volume control. In order to facilitate a clem understanding of the invention, it will be described in terms of such an application.-

, Referring now to FIG. 1, audio signal source 10 cancomprise a radio receiver, a public address system, or in general, any system capable of producing electrical signals in the audio range. Such signals are supplied to a speaker 11 through the transformer 12 and the switching circuit enclosed in the block 13. It is this switching circuit which constitutes the invention.

The switching circuit is composed of two sections 21 and 22 of which section 22 can be located near the speaker 11 and of which section 21 can be located at a point remote from the speaker, as, for example, in an operators hand across the'room from the speaker. Alternatively the section 2.1 can be located near the speaker and, in turn, can be controlled by some means located at a point remote from the speaker.. ln'the section 22, the resistor 14 is connected in series with the speaker impedance 29. Single pole, double throw switch 16 which comprises stationary contacts 18 and 19 and movable contact 17, is constructed and arranged so that when contact 17 is closed on contact 1%, the section 21 can have no eliect on the amount of power supplied to the 7 speaker 11 since there can be no complete circuit between sections 21 and 22'.

However, when the movable contact 17 is closed on the contact 1% (remote control position) a complete circuit is created between the sections 21 and 22 regardless of the position of movable contact 23 of the section '21.-

More specifically, when the movable contact 23 is closed on stationary contact A the resistor 14 is shunted by a circuit including conductor 24, movable contact 23, con ductor 26, and movable contact 17. When the movable contact 23 is "closed on stationary contacts B, C, and D there is respectively, a 5.6 resistance (resistors 27 and 28), a 1 ohm resistance (resistor 28), and a short circuit through conductor 41, placed in parallel with the speaker winding 23.

It will be apparentthat when movable contact 23 is closed on contact A, the full power output from the audio signal source 10 will be supplied to the speaker 23 and Patented May 8, 1962 that when the movable contact is closed on contacts B and C, decreasing amounts of power are supplied to the speaker 11. In position D, of course, no power is supplied to the speaker. i

The values of the resistors 27 and 28 and resistor it are selected so that the overall impedance looking into the terminals 31 stays within fairly close limits for any combinations of positions of movable contacts 17 and 23. Since this overall resultant impedance is fairly close to the impedance of the Speaker ill, signal distortion can be kept at a minimum for all of the volume levels.

With a speaker impedance of 3 ohms, with resistors 27 and 23 having values of 4.6 ohms and 1 ohm respectively, and with movable contact 17 closed on remote position contact 18 the impedances presented to the terminals 31 as the movable contact 23 is closed on contact positions A through D are as follows.

Referring now to FIG. 2, there is represented an alternative form of the circuit within the block 21 in which parallel arranged resistors 32 and 33 are employed in lieu of the series arrangementshown in the block 21 of FIG. 1. The leads 2%, 26', and 41' of FIG. 2 connect to the same points as the corresponding leads 24, 26 and 41 of FIG. 1. In its operation, the circuit of FIG. 2 is the same as the circuit of FIG. 1. g

In the previous descriptive material, it has been assumed that the portion of the circuit within the blocks Zlof FIG. l or 2.1 of FIG. 2 would be located at a point remote from the television, radio, or. other speaker to enable an operator to control the volume from such remote point.

However, owing to the fact that section 21 contains only one movable contact (23), it has been found convenient to locate the section 21 in the receiver being employed and to operate the movable contact 23 by some be constructed, in response to an act of an operator, to

produce sonic waves or electrical waves, or may even bev connected to a receiver-transducer 37 by conductors, can be located remotely from .the section 21". Receivertransducer 37 is constructed to respond to the output signal 36 ofsaid transmitter to produce a signal which will operate stepping switch 38. Stepping switch 38 is linked mechanically with the movable contact 23:" so that with each step of the stepping switch 38, the movable contact 23" will rotate to disengage with a given one of contacts A", B", C, or D and to close on the next consecutive contact.

Referring now to the circuit of FIG. 4, there is shown an alternative form of the circuit of FIG. 1. The end terminal of the resistor 28" is connected directly to a terminal of the speaker through conductor 41' and the stationary contact D is connected to the control grid of an audio amplifier tube (not shown), thus grounding said control grid and preventing any audio signal from reaching speaker 11.

More specifically the aforementioned control grid will be grounded, when movable contact 23" is closed on contact D, in a circuit extending through conductor 40, movable control 23", conductor 26, movable control 17, and the speaker winding 29.

A stepping switch suitable for use herein is described in application Serial Number 739,324, filed June 2, 1958, now US. Patent No. 2,990,723 of July 7, 1961, by Clarence J. Holpuch and entitled Stepping Switch, and which is incorporated herein as a part of this specification.

It is to be noted that the forms of the invention herein shown and described are but preferred embodiments thereof and that various changes can be made therein without departing from the spirit or scope thereof.

We claim:

1. In combination; a source of electrical signals; a transducer for converting said signals into acoustic energ]; a transformer coupling said source to said transducer, one lead of said transformer being directly connected to one lead of said transducer; a first resistor'serially connected between the other lead of said transformer and the other lead of said transducer; a switching network connected in parallel with said first resistor, said switching network including a switch having a plurality of switching positions; and means in said switching network for placing an electrical short circuit about said first resistor when said switch is in saidfirst position, where by no signal. attenuation is experienced by said transducer, and for removing said electrical short circuit and introducing successive combinations of series and parallel resistances, each including said first resistor, between said source and said transducer when said switch is moved to successive ones of said plurality of switching positions, whereby the power available to said transducer is successively varied.

2. The combination of claim 1, wherein one of said successive ones of said plurality of switching positions includes a connection to said one lead of said transducer whereby a direct short circuit is placed across said transducer.

3. In combination; a source of electrical signals including an output transformer having two leads; a transducer for converting said electrical signals into corresponding acoustic signals, said transducer also having two leads; a common connection between one lead of said transformer and one lead of said transducer; a first resistance element serially connected between the other lead of said transformer and the other lead of said transducer; a single pole switch, having a movable contact making arm and a plurality of stationary contact positions, arranged with said arm connected to said other lead of said transducer; a first one of said stationary contacts being connected to said other lead of said trans former; a second resistance element connected between a second and a third one of said stationary contacts; a

direct connection between said third stationary contact and said common connection; whereby, when said arm rests on said first contact said first resistance element is short circuited and said transducer is connected directly across said source, when said arm rests on said second contact said second resistance element is connected in parallel with said transducer and the combination cona substantially constant impedance match with the power' source comprising; a power source; a load; first resistor means electrically connected between one terminal of said power source and one terminal of said load; a common connection between the other terminal of said power source and the other terminal of said load; second resistor means electrically coupled to said common connection; a first switch having a first movable contact electrically connected to said one terminal of said load; a second multiple contact switch having a second movable contact; said first movable contact of said first switch being movable between a first position in which said first resistor means is short circuited and a second position in which said short circuit is removed and said first movable contact is electrically connected to said second movable contact; said second resistor means comprising a plurality of resistor elements; said second movable contact being 5 movable between a position in which it is electrically connected to said one terminal of said power source and a plurality of positions in which its movable contact is electrically connected to selected ones of said resistor elements whereby said selected resistor elements may be arranged in parallel with said load when said first movable element of said first switch is in its second position.

UNITED STATES PATENTS Smith Dec. 19, 1939 FOREIGN PATENTS Italy Feb. 11, 1953 Great Britain July 17, 1957 

